Electrical safety system for electrical device

ABSTRACT

Apparatus and electrical circuitry are provided for electrical devices in order to provide electrical isolation of exposed electrical contacts on at least one of multiple modules of the electrical device. The apparatus includes at least one actuating component in one module and at least one sensor component within a second module in electrical communication with electrical circuitry, whereby electrical isolation of the exposed electrical contacts ceases when the sensor apparatus senses a desired location of the module. Placement of the apparatus and electrical circuitry to reside within the modules promotes electrical safety while minimizing tampering with safety aspects of the device. The apparatus and circuitry are useful for medical devices such as handheld diagnostic devices and consumer devices such as telephones.

This is a continuation of application Ser. No. 08/008,724, filed Jan.22, 1993, abandoned.

FIELD OF THE INVENTION

This invention relates to an electrical safety system for electricaldevices, and especially for medical devices to be used in the proximityof health care practitioners and patients.

BACKGROUND OF THE INVENTION

An electrical device, such as a medical device requiring the use ofelectricity, must comply with certain electrical safety requirements inorder to achieve listing with organizations that review the safety ofelectrical products. A concern present for any medical device is tominimize the possibility of electrical shock caused by exposure toelectrical contacts used as part of the medical device. This concern hascaused the art to develop electrical circuitry such as isolationamplifiers and the like to minimize the exposure of the patient andhealth care practitioner to electrical voltage and current. See, forexample, U.S. Pat. No. 4,803,996 (Peel et al.).

Other electrical circuitry has been developed in the circumstance whenthe medical device comprises two or more separable modules which requireelectrical contact when the modules are mated for battery-powered use.See, for example, U.S. Pat. No. 4,578,628 (Siwiak), which uses switchingand fusing means to assure proper interconnection between a battery packand its mateable radio portion and avoidance of inadvertent shortcircuits of the battery terminals.

Medical device market suppliers and users, in conjunction withUnderwriters Laboratories, have developed safe operating performancecriteria for medical apparatus that limit exposed electrical contact ofapparatus to an extremely small electrical current should a person comein contact with these exposed contacts. Currently, the UnderwritersLaboratories Standard for Safety 544 sets a limit of 50 microamps fordouble insulation circuits and otherwise 100 microamps.

Electronic medical devices often must be made small and portable.Examples include stethoscopes and other diagnostic systems, electronicprosthetic devices such as transcutaneous electrical nerve stimulators,and patient monitoring equipment. While this list is not exclusive, itgenerally indicates the problems which are associated with designing andproducing small, portable electronic medical devices.

Requirements for such electronic medical devices can include alight-weight, portable diagnostic device having a self-contained powersource (often a rechargeable battery) capable of easy and safeoperation. Stationary accessory operations for such electronic medicaldevices typically include battery recharging apparatus and circuitry anddata communication to associated computers, instruments and equipment.The mechanical alignment and electrical interconnection between theportable device and the stationary device must be convenient and safe inthe critical hospital and clinical environments. These requirements areespecially true of electronic stethoscopes and portable, hand helddiagnostic tools such as cardiac and pulmonary auscultation detectorsand graphic display apparatus.

Two examples of portable electronic medical devices having multiplemodules comprising a portable diagnostic module and a stationarysupporting module include stethoscopes and associated equipmentdisclosed in U.S. Pat. No. 5,010,889 (Bredesen et al.) and pending U.S.patent application Ser. No. 07/782,079 (Bredesen et al.), thedisclosures of which are incorporated by reference.

Exposed electrical contacts are often required for making effectiveconnections between portable devices and associated support equipment,such as a portable medical device containing a battery and theassociated battery charger. Electrical safety can be achieved in variousways. Some prior efforts have included limiting the level of operatingvoltage, (e.g., operating below a certain threshold such as 40 volts)under carefully specified conditions as covered by Standard 544 fromUnderwriters Laboratories, Inc., Northbrook Ill. or providing insulationor clearances that limit leakage current to low levels and limit exposedcontact points to voltages below specified levels.

SUMMARY OF THE INVENTION

The invention provides both apparatus and circuitry for electricalisolation of exposed contacts on at least one of multiple modules ofelectrical devices when such contacts are not in use. Electricalisolation can include either electrical disconnection or electricalgrounding, or both, as the electrical device may require for safetypurposes. The invention also provides means for connecting contactpoints to active electrical circuitry only during the time that there isproper mechanical alignment between two modules of a medical device. Anonlimiting example of two modules of a medical device is a portablediagnostic device separably electrically connected to and mechanicallyaligned in proximity to stationary support equipment which is typicallyconnected to an electrical line power.

In another aspect of the present invention, apparatus and circuitrymeans for switching the electrical circuit is provided where theapparatus and circuitry is controlled only by positioning the portabledevice in proper orientation with, and in proximity to, the supportequipment device by means of a system that is not apparent to the useror subject to user intervention.

In another aspect of the invention, the apparatus and circuitry meansonly energizes the electrical contact points after mechanical alignment.The contact points reside at a location of the portable module'smechanical alignment with the stationary support equipment, such that ahealth care practitioner or a patient is protected from exposure to suchenergized electrical contact points.

The invention provides an apparatus for electrical isolation of exposedelectrical contacts on at least one of multiple modules of an electricaldevice. The apparatus comprises at least one sensor component within atleast one module in electrical communication with electrical circuitry,whereby electrical isolation of the exposed electrical contacts ceaseswhen each sensor component senses a desired location of the module andthe exposed electrical contacts become energized.

The invention also provides an electrical circuit for electricalisolation of exposed electrical contacts on at least one of multiplemodules of electrical devices. The circuit comprises at least oneelectrical switching device in electrical communication with at leastone sensor component within one module, whereby electrical isolation ofthe exposed electrical contacts ceases when the sensor component sensesa desired location of the module and at least one switching devicecloses.

A feature of the invention is the economical employment of apparatus andcircuitry within the stationary support equipment which isself-contained and promotes safety.

Another feature of the invention is the provision of the circuitry tomaintain open circuits unless and until there is proper mechanicalalignment contact between the portable module and the stationary supportequipment. In that manner, the electrical isolation of exposedelectrical contacts on at least one module of the device is maintaineduntil the electrical isolation ceases due to proper mechanicalalignment.

An advantage of the invention is that the likelihood of exposed,energized, electrical contacts on the stationary support equipment isminimized to the circumstance when the portable module is in propermechanical alignment and in electrical interconnection. The portablemodule in proper mechanical alignment then shields the energizedcontacts from exposure.

The foregoing advantages, construction and operation of the presentinvention will become more readily apparent from the followingdescription and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a medical device including astethoscope, a portable display module, a stationary printer/chargermodule, and electrical line power source (including a transformer)utilizing the present invention.

FIG. 2 is a perspective view of the display module and theprinter/charger module showing exposed electrical contact pairs.

FIG. 3 is a perspective view with a partial cutaway of the displaymodule showing the actuator component for the safety system injuxtaposition with a partial cutaway of the printer/charger moduleshowing the safety switching components.

FIG. 4 is a perspective of the actuator and sensor showing the relativeoperational orientation.

FIG. 5 is a electrical circuit schematic detailing the safety switchingcircuitry and its relationship to functional elements of the medicaldevice.

EMBODIMENTS OF THE INVENTION

Electrical devices useful with the apparatus of the present inventioncan be electrical devices where a first module is portable andrechargeable, and the second module is stationary and electricallyconnectable to line power. Nonlimiting examples of electrical devicesinclude handheld consumer devices (such as flashlights, electric razors,electronic control units, cordless and cellular telephones, andportable, electrical hand tools), larger portable electrical equipment(such as lawn and garden equipment), and other modules requiringtemporary electrical connection to a stationary module.

Preferably, electrical devices are medical devices where portability ofhandheld diagnostic equipment is desirable. The medical device shown inFIG. 1 is a graphical auscultation system 10 to be used by doctors orother medical practitioners for the acquisition, display, storage andanalysis of body sounds, particularly heart sounds. Nonlimiting examplesof such auscultation instrumentation are graphic display stethoscopesdisclosed in U.S. Pat. No. 5,010,889 (Bredesen et al.) and pending U.S.patent application Ser. No. 07/782,079 (Bredesen et al.), thedisclosures of which are incorporated by reference.

The system 10 includes stethoscope 3 which the health care practitioneruses to select the appropriate sound location and characteristic.Integral to the stethoscope 3 is a transducer (not shown) which convertsthe acoustical signal to an electrical signal. The electrical signal iscommunicated by means of cable 4 to the portable, hand held displaymodule 1. The display module 1 may include a complex electronicprocessing circuitry as well as a liquid crystal or other display andmemory and other electrical components, all powered by an internalbattery, preferably a rechargeable battery.

Electrical and data communication and other support service for theportable display module 1 is provided from the printer/charger module 2which is powered from a standard electrical line power source 5 througha connecting cable 6. Further, communication to other devices such as acomputer printer, a personal computer or other accessories (all notshown) can be made through interconnection cable 7.

The stationary printer/charger module 2 is readily accessible and madeelectrically safe for use by means of the present invention. FIG. 2shows detail of the electrical interconnection of the display module 1and printer/charger module 2. Electrical contact pairs 21-22 and 23-24are data communication connections and contact pairs 25-26 and 27-28 arethe battery charging connections. Electrical contact is made betweenthese respective contact pairs when the display module 1 is properlymechanically aligned, e.g., positioned and seated into recess 20 of theprinter/charger module 2.

In preferred use, the printer/charger module 2 is connected to linepower by cable 6 and power source 5 and to remote equipment throughcable 7.

According to the invention, connector contacts 21, 23, 25, and 27 areelectrically isolated from the other circuitry of the printer/chargermodule at all times except when the display module is seated in theprinter/charger module 2 for charging and/or data transfer.

Preferably, the electrical isolation is accomplished by providingswitching devices, (e.g., solid state switches, electrical relays, andthe like) As shown in FIG. 3, normally open electrical relays 34 and 35are provided in the electrical circuit of the printer/charger module 2in electrical communication with contacts 26 and 28, and 25 and 27,respectively.

Operation of relays 34 and 35 to close electrical circuitry betweenprinter/charge module 2 and display module 1 is accomplished by a sensorcomponent 33 which is only operative by properly seating the displaymodule 1 in the printer/charger module 2, thereby aligning actuatingcomponent 36 with the sensor 33. Electrical isolation ceases whennormally open relays 34 and 35 close.

Preferably, the sensor component 33 is a magneto-resistive sensormounted on a electrically insulating circuit board 32 withinprinter/charger module 2. Preferably, the actuating component 36 is apermanent magnet mounted on a electrically insulating circuit board 38in the display module. Specifically the magnet is model 102MG15 magnetand the magneto-resistive digital position sensor is a model 2SSPsensor, both commercially available from Micro Switch Division ofHoneywell Inc., Minneapolis Minn. The relative magnetic alignment ofthese components is shown in FIG. 4 wherein the magnet 44 is positionedin a plane parallel to the plane of the magneto-resistive sensor 42 andaligned with the sensor. Magnet 44 can be oriented in either polarity.Preferably, arrow 46 indicates the locus of influence of the magnetfield. The sensor-to-magnet operational range is approximately 2.5 cm orless, and preferably 0.5 cm when the modules 1 and 2 are in properalignment.

Preferably, the apparatus and circuitry are contained within the modulesand concealed from sight. Thus, no part of the safety system is apparentto the user. Thus, operation of the safety system it is not readilyapparent to the user making it difficult to override or circumvent thesafety system. Further, the use of obscured magnetic components reducesthe possibility of overriding the safety system with commonly availablematerials applied to the exterior of either module 1 or 2. Materials,such as tape, string, or adhesives could otherwise restrain exteriorcomponents in undesired positions for unsafe use. Procedures such asusing a wire cutter for disconnecting exterior components are minimizedby use of the safety system of the present invention.

Numerous combinations of actuating component 36 and sensor component 33can be used in place of the presently preferredmagneto-resistive/permanent-magnet combination. Nonlimiting examplesinclude magnetic Hall-effect sensor/permanent-magnet,reed-switch/permanent-magnet, optical switch/light emitting diode (LED)light source, magneto-dynamic transformer, electro-static capacitivecoupling, electro-dynamic capacitive coupling, and radio frequencycoupling, or other solid state sensors. Further, multipleactuator-sensor pairs could be used in selected geometric configurationand/or selected switching logic configuration to provides successivelyhigher security levels through successively more specific positioning ororder of positioning events.

Multiple sensor components and multiple actuator components also can beemployed in either or both modules according to desired advantages,e.g., to use multiple sensor components and actuator components toidentify and recognize differentiated modules for specific interactionbetween modules; and to use multiple sensor components in one module todifferentiate among different actuator components in different matingmodules. In that respect, use of multiple sensor components and multipleactuator components provides an additional level of safety control orcommunication technique, or both.

FIG. 5 is detail of the circuit schematic of a preferred embodimentutilizing the magneto-resistive element 33 to control normally openrelays 34 and 35. The relays are 2 pole normally open contact typedevices, model JWD-171-23 relays commercially available from Potter andBrumnfield, Chicago Ill. The relays are separated electrically forassured isolation.

Relay 34 controls the charging circuit, which electrically connectscharging contacts 27 and 28 with power supply 54. Supply 54 is connectedto a external source of electrical power at 56.

Relay 35 controls the information circuit, which electrically connectscontacts 21 and 22 with processing and control system 52. System 52 canbe connected to external equipment such as a printer or a personalcomputer at 58.

Relays 34 and 35 are controlled by a single sensor component 33,although multiple combinations of sensor component 33 and actuator 36can be provided to add a variety of safety or communications features,or both, to the electrical circuitry.

Relay 34 is positioned electrically and physically close to contacts 25and 26 and relay 35 is positioned electrically and physically close tocontacts 21 and 23 to minimize cross-talk and leakage current from otherparts of the electrical circuitry. Table 1 is the component listing ofFIG. 5.

TABLE 1

DS1--Panasonic LED LN28RP

D29, D30--1N4148 Diode

DSP1--Honeywell 2SSP Sensor

K1, K2--Potter and Brumnfield JWD-171-23 Relay

Q1--Philips MPSA56PH Transistor

R2--330 ohm Resistor

R23--2.7 K ohm Resistor

R24--100 K ohm Resistor

R25--1.5 K ohm Resistor.

While an electrical isolation safety system has been described for usein the printer/charger module 2, it is within the scope of the presentinvention to provide a complementary or supplementary electricalisolation safety system in the display module 1. Sensors and actuatorcan be provided in the opposite modules to the positions shown in FIG. 3for duplicative or supplementary effect for isolation of the exposedcontacts of the portable diagnostic device for further safetyprecaution.

The scope of the invention is identified in the following claims.

What is claimed is:
 1. An apparatus for electrical isolation from apower source of exposed electrical contacts on multiple modules of anelectrical device, wherein the isolation continues until properalignment of the multiple modules, wherein the device comprises twomodules capable of mechanical alignment and electrical connection, andwherein at least one module is portable,the apparatus comprising:unenergized, exposed electrical contacts on the first module, at leastone concealed actuating component within the first module, at least oneconcealed sensor component within the second module, unenergized,exposed electrical contacts on the second module, and at least oneelectrical switching device in electrical communication with acorresponding concealed sensor component and with the power source,wherein each switching device is normally open but when closed is inelectrical communication with corresponding exposed electrical contactson the second module and in energized electrical communication withelectrical circuitry connected to the power source, wherein alignment ofa concealed actuating component and a corresponding concealed sensorcomponent causes a corresponding switching device to close and toprovide energized electrical communication with electrical circuitry tothe exposed electrical contacts on the second module, and whereinmechanical alignment of the first module and the second module causesenergized electrical connection of exposed electrical contacts on thesecond module with corresponding exposed electrical contacts on thefirst module.
 2. The apparatus according to claim 1, wherein each sensorcomponent is a magneto-resistive position sensor, wherein each actuatingcomponent is a magnet, and wherein the alignment is a magneticalignment.
 3. The apparatus according to claim 1, wherein eachelectrical circuitry switching device comprises an electrical relay. 4.The apparatus according to claim 3, wherein each electrical relay iselectrically connected to an exposed electrical contact when theelectrical isolation ceases because of alignment of an actuatingcomponent and a sensor component that causes a corresponding relay thatis normally open to close.
 5. The apparatus according to claim 1,wherein the electrical circuitry communicates information between thefirst module and the second module when the electrical isolation ceasesand when the two modules are in mechanical alignment and electricalcommunication.
 6. The apparatus according to claim 1, wherein theapparatus comprises multiple actuator components and multiple sensorcomponents.
 7. The apparatus according to claim 1, wherein each sensorcomponent comprises a magnetic Hall-effect sensor or a reed switch,wherein the actuating component is a magnet, and wherein the alignmentis a magnetic alignment.
 8. The apparatus according to claim 1, whereineach sensor component is an optical switch, wherein each actuatingcomponent is a light emitting diode, and wherein the alignment is anoptical alignment.
 9. The apparatus according to claim 1, wherein eachsensor component and each actuating component comprise a magneto-dynamictransformer coupling.
 10. The apparatus according to claim 1, whereineach sensor component and each actuating component comprise anelectro-static capacitive coupling.
 11. The apparatus according to claim1, wherein each sensor component and each actuating component comprisean electro-dynamic capacitive coupling.
 12. The apparatus according toclaim 1, wherein each sensor component and each actuating componentcomprise a radio frequency coupling.
 13. The apparatus according toclaim 1, wherein the electrical device is a medical device.
 14. Theapparatus according to claim 1, wherein the medical device is a handhelddiagnostic device.
 15. An electrical circuit for electrical isolationfrom a power source of exposed electrical contacts on multiple modulesof an electrical device, wherein the device comprises two modulescapable of mechanical alignment and electrical connection, wherein atleast one module is portablethe electrical circuit comprising:unenergized, exposed electrical contacts on the first module,unenergized, exposed electrical contacts on the second module; at leastone electrical switching device normally open and interposed between thepower source and the exposed electrical contacts on the second module;at least one concealed sensor component within the second module inelectrical communication with the electrical switching device; at leastone concealed actuating component in the first module; wherein eachelectrical switching device closes when a corresponding concealed sensorcomponent reacts to an alignment of a corresponding concealed actuatingcomponent when the first and second modules are brought into mechanicalalignment; wherein each closed electrical switching device is inenergized electrical communication with electrical circuitry connectedto the power source and in energized electrical communication withcorresponding exposed electrical contacts on the second module forenergized electrical communication with the exposed electrical contactson the first module.
 16. The electrical circuitry according to claim 15,wherein each electrical circuitry switching device comprises anelectrical relay.
 17. The electrical circuitry according to claim 16,wherein the electrical circuitry communicates information between thefirst module and the second module when the electrical isolation ceasesand when the two modules are in mechanical alignment and electricalcommunication.